Hitchhiking Herpes Virus Aligns with Spread of Human Civilization

A genomic study of the herpes simplex type 1 virus has revealed marked parallels with the migration of humans over the course of civilization.

Researchers behind the study say the results are a confirmation of the "out-of-Africa" pattern of human migration, which has previously been documented by anthropologists and by studies of the human genome.

Curtis Brandt, a professor of medical microbiology and ophthalmology at the University of Wisconsin-Madison, and his colleagues collected 31 samples of different strains of herpes simplex type 1 (HSV-1), with origins North America, Africa, Europe and Asia.

After analyzing the different strains, "the result was fairly stunning," Brandt said.

"The viral strains sort exactly as you would predict based on sequencing of human genomes. We found that all of the African isolates cluster together, all the virus from the Far East, Korea, Japan, China clustered together, all the viruses in Europe and America, with one exception, clustered together," he said, adding that there "was clear support for the out-of-Africa hypothesis. Our results clearly support the anthropological data, and other genetic data, that explain how humans came from Africa into the Middle East and started to spread from there.

"What we found follows exactly what the anthropologists have told us, and the molecular geneticists who have analyzed the human genome have told us, about where humans originated and how they spread across the planet," he said.

Brandt and his colleagues, who published their work in the journal PLOS One, used a series of high-capacity genetic sequencing tests and and advanced bioinformatics to analyze the huge amount of data presented by 31 HSV-1 genomes.

The researchers broke in the individual virus genomes into 26 pieces and made family trees for each piece, then combined each of the "trees" into one larger tree that represented the whole genome. By plotting the genes in such a way, the researchers were able to see even more links to migration embedded within the genomic code.

All but one of the HSV-1 samples from the United States matched the European strains. The lone strain was found in Texas; it looked Asian. The researchers suggest that it could have come to Texas by way of someone who had traveled to the Far East, or perhaps, it came from a native American whose ancestors had crossed the "land bridge" across the Bering Strait roughly 15,000 years ago.

"We found support for the land bridge hypothesis because the date of divergence from its most recent Asian ancestor was about 15,000 years ago. Brandt says. "The dates match, so we postulate that this was an Amerindian virus."

Brandt said a similar analysis of deadly viruses could shed new light on why certain strains of a virus are so much more lethal than others.

"We'd like to understand why these few viruses are so dangerous, when the predominant course of herpes is so mild. We believe that a difference in the gene sequence is determining the outcome, and we are interested in sorting this out," he said.